Classic animal work in sleep science has established that adequate sleep with regard to duration and quality is required for normal cognitive performance during waking periods. In humans, “good” sleep is required for the consolidation of long term memory of the previous day's experiences. The interruption of this process by poor sleep may be an important determinant of why patients with mild Traumatic Brain Injury (mTBI) deteriorate in work and general performance over time, and may experience emotional or psychiatric consequences. Past studies have extensively quantified the striking relationships that neurocognitive performance deficits, sleep deprivation, and sleep loss have to sleep disorders associated with brain injuries.
Human studies have confirmed that quantitative measures of sleep deprivation parametrically predict cognitive performance decrements in normal and brain injured patients. The mechanistic model: A. brain injury→B. sleep disorders→C. sleep loss→D. decreased daytime alertness→E. cognitive deficits, is supported by experimental literature on sleep loss/cognitive performance decrement. As described above, it is well known that sleep disorders lead to accumulation of sleep debt correlated with diminished daytime functioning. Of particular interest is the detection of sleep disorders consequential to suspected mTBI at step B of the model, before “allostatic compensation” for accumulated sleep loss is exhausted, and alertness and cognitive functions are compromised.
In January 2008, the US Department of Defense reported a total of 5,503 soldiers currently suffering with traumatic brain injuries. Mild Traumatic Brain Injury is the most common kind of combat injury, frequently leading to cognitive deficits in attention, speed of information processing, and working long-term memory performance. As many as 30% of patients with mTBI show neurological symptoms such as, for example; headaches, dizziness, irritability, and neurocognitive deficits, long after experiencing head trauma.
Neurocognitive deficits are commonly found in patients with mTBI, as are complaints of sleep disorders, daytime sleepiness and fatigue in 70% of cases during the first six months after experiencing a concussion. It is well known that brain injury, including traumatic brain injury, is commonly accompanied by sleep disturbance and, over a short period of time, consequent sleep deprivation. As is well established, sleep deprivation leads to parametric dose-related loss of cognitive executive function, fatigue, and mood problems.
Although most cases of mTBI resolve within six to twelve months, 20-30% of patients with mTBE have persistent symptoms, most commonly headache and sleep disorders. The main symptom cluster is complaint of cognitive impairment, e.g., deficits of attention, information processing speed, working and long-term memory loss. Pharmacological, cognitive, and behavioral treatment for mTBI have had mixed success to date and mTBI has been found to be resistant to neuropsychological rehabilitation.
Early detection is critical to insure the safety of a patient with mTBI, as well as others who are dependent on the patient's functioning. Persistent cognitive fog and sleep disorders may lead to psychiatric, work, and family functional impairment. Recent studies report that cognitive confusion, memory loss, and psychiatric symptoms predict risk for a second TBI and further complicate the rehabilitative process.
While even mild brain trauma has been shown to cause neuronal damage, brain injury detection during the early post-concussive period continues to be difficult. Current screening methods with magnetic resonance imaging to establish neurological correlations of mTBI cognitive deficits have produced results that are lower than expected. The need for better screening is appreciated and new techniques are currently being developed. Axonal damage has recently been reported using diffusion tensor imaging and it is hoped that the technology may improve objective screening capabilities in the future.
Diagnosis of brain injury, particularly mTBI, or concussion as it is commonly known, is typically performed by combining imaging technology with established techniques for assessing consciousness and/or cognitive function. A conclusion of brain injury is made based on the sum of results. The Glasgow Coma Scale (GSC) is recognized as one of several reliable means for assessing the level of consciousness in subjects known to have received head injuries. The assessment tool records eye opening behavior along with verbal and motor responses to arrive at a cumulative score indicative of the level of brain injury. Patients with scores less than 14 are considered to be affected by minor brain injury. Scores of less than 13 and 9 represent moderate and severe brain injury, respectively. While GCS is a useful tool, combining brain images with only GCS scoring has proven inadequate for screening. Behavioral functioning as measured by GCS may be normal for up to a week after the injury event. Furthermore, even when early GCS scores are indicative of brain injury, too much emphasis may be placed on the complementary technologies. Accordingly, false negative screening conclusions are common despite low early GCS scores.
Thus, objective screening for mTBI is often inconclusive, particularly in the acute phase of post-trauma. Delayed diagnosis and treatment of early stage brain injury prolongs patient recovery and cognitive rehabilitation. Early detection of developing impairment is essential for intervention purposes. While monitoring changes in sleep behavior has had the potential to identify patients inflicted with brain injury that have been mischaracterized by conventional screening technology, systems and methods of screening, carefully designed to discriminate patients with traumatic brain injury from patients suffering merely from non-trauma related sleep complications, have yet been unavailable. Therefore, to overcome the shortcomings currently existing in the art, an innovative system to efficiently and reliably differentiate relatively normal sleep movement patterns from those of persons afflicted with early stage brain injuries such as mTBI following head trauma is needed.